1. Field of the Invention
The present invention relates to a toner, and to a developer, an image forming method and a process cartridge using the toner.
2. Description of the Related Art
There are a number of electrophotographic image forming methods. Such electrophotographic image forming methods typically include the following processes:
(1) Forming an electrostatic latent image on an image bearing member including a photosensitive material such as a photoreceptor (latent image forming process);
(2) Developing the electrostatic latent image with a developer including a toner to form a toner image on the image bearing member (developing process);
(3) Transferring the toner image onto a recording material such as paper (transferring process);
(4) Fixing the toner image on the recording material upon application of heat, pressure, a combination of heat and pressure, a vaporized solvent, or the like, resulting in formation of an output image (fixing process); and
(5) Cleaning the surface of the image bearing member to remove residual toner particles therefrom (cleaning process).
A particulate material having an average particle diameter on the order of from a few nanometers to tens of micrometers is used as an external additive of conventional toners. In attempting to impart a good combination of charging property, fluidity and hydrophobicity to toner, a hydrophobized particulate silica is typically used as an external additive, and a hydrophobized titanium oxide is used in attempting to decrease variation of chargeability and charge quantity of toer caused by change of environmental conditions.
In attempting to improve stability and performance of electrophotographic image forming apparatus, toner including two or more of these external additives has been used for the image forming apparatus while adjusting the mixing ratio thereof.
Recently, various modifications have been performed on the main body (i.e., mother toner or toner particles) of toner in attempting to improve the properties of the toner. Specific examples of such modifications are as follows:
(1) The amount of a wax included in toner particles is increased so that the wax is used efficiently (i.e., a good releasability is imparted to the toner) when the toner is fixed;
(2) A wax is mainly included in a surface portion of toner particles so as to be used efficiently when the toner is fixed; and
(3) A crystalline material is included in toner particles so that the toner can be easily melted in a fixing process with relatively low heat energy.
Such modified toners (1) and (2) tend to cause a phenomenon in which a wax included in toner particles exudes from the toner particles when environmental conditions and conditions of the image forming apparatus change, thereby deteriorating the properties of the toner and the developer, resulting in deterioration of image quality. The modified toner (3) tends to cause a phenomenon in which an alcohol component used for preparing such a crystalline material remains in the toner particles in a small amount, thereby deteriorating the property of the toner.
For these reasons, there is a need for a toner which can produce high quality images for a long period of time without causing such a wax and/or alcohol exuding phenomenon as mentioned above.